U.S. patent number 6,360,717 [Application Number 09/638,634] was granted by the patent office on 2002-03-26 for fuel injection system and a method for operating.
This patent grant is currently assigned to Caterpillar Inc.. Invention is credited to David Y. Chang, David C. Mack.
United States Patent |
6,360,717 |
Chang , et al. |
March 26, 2002 |
Fuel injection system and a method for operating
Abstract
The present invention provides a fuel injection system and
method of operating the fuel injection system. The fuel injection
system includes at least one hydraulically actuated fuel injector
fluidly connected with a source of high pressure actuation fluid. A
viscosity sensor determines the viscosity of the hydraulically
actuated fuel injector. A controller in communication with the fuel
injector and the viscosity sensor is configured to determine the
rate of change of the viscosity of the high pressure hydraulic
actuation fluid. The supply of high pressure actuated fluid to the
fuel injector is based, at least in part, on the rate of change of
the determined viscosity of the high pressure actuation fluid.
Inventors: |
Chang; David Y. (Savoy, IL),
Mack; David C. (Pontiac, IL) |
Assignee: |
Caterpillar Inc. (Peoria,
IL)
|
Family
ID: |
24560827 |
Appl.
No.: |
09/638,634 |
Filed: |
August 14, 2000 |
Current U.S.
Class: |
123/381;
123/494 |
Current CPC
Class: |
F02D
41/3809 (20130101); F02M 57/025 (20130101) |
Current International
Class: |
F02M
57/00 (20060101); F02M 57/02 (20060101); F02D
41/38 (20060101); F02M 037/04 () |
Field of
Search: |
;123/446,381,494 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moulis; Thomas N.
Attorney, Agent or Firm: Cheek; John J.
Claims
What is claimed is:
1. A method of operating a fuel injection system including at least
one hydraulically actuated fuel injector fluidly connected with a
source of high pressure actuation fluid, the method comprising the
steps of: determining the viscosity of the high pressure actuation
fluid; determining a rate in change of the viscosity of the high
pressure actuation fluid; and, controlling the supply of high
pressure actuated fluid to the fuel injector based, at least in
part, on the rate of change of the determined viscosity of the high
pressure actuation fluid.
2. A method, as set forth in claim 1, the fuel injector being
located in an engine, wherein the step of determining a rate of
change of the viscosity of the high pressure actuation fluid
further comprises the steps of: determining a rate of fuel
consumption; determining an engine operating condition; and,
dynamically calculating the rate of change of the viscosity of the
high pressure actuation fluid based on the rate of fuel consumption
and the engine operating condition.
3. A method, as set forth in claim 1, the fuel injector being
located in an engine, wherein the step of determining a rate of
change of the viscosity of the high pressure actuation fluid
further comprises the steps of: determining a rate of fuel
consumption; determining an engine operating condition; comparing
the rate of fuel consumption and the engine operating condition
with at least one of a plurality of maps; and determining the rate
of change of the viscosity of the high pressure actuation fluid in
response to the comparison.
4. A method, as set forth in claim 1, the fuel injector being
located in an engine, wherein the step of determining a rate of
change of the viscosity of the high pressure actuation fluid
further comprises the steps of: determining a rate of fuel
consumption; determining an engine operating condition; comparing
the rate of fuel consumption and the engine operating condition
with at least one of a plurality of tables; and determining the
rate of change of the viscosity of the high pressure actuation
fluid in response to the comparison.
5. A method, as set forth in claim 1, further comprising the step
of determining a shear rate adjustment of the high pressure
actuation fluid.
6. A method, as set forth in claim 5, the fuel injector being
located in an engine, wherein the step of determining a shear rate
adjustment of the high pressure actuation fluid further comprises
the steps of: determining an engine load; comparing the temperature
of the actuating fluid with at least one of a plurality of shear
rate tables and responsively selecting a shear rate table; and,
determining the shear rate adjustment in response to the viscosity
of the high pressure actuation fluid, the engine load, and the
selected shear rate table.
7. A method, as set forth in claim 5, the fuel injector being
located in an engine, wherein the step of determining a shear rate
adjustment of the high pressure actuation fluid further comprises
the steps of: determining an engine load; comparing the temperature
of the actuating fluid with at least one of a plurality of shear
rate maps and responsively selecting a shear rate map; and,
determining the shear rate adjustment in response to the viscosity
of the high pressure actuation fluid, the engine load, and the
selected shear rate map.
8. A fuel injection system, comprising: a source of high pressure
actuation fluid; at least one hydraulically actuated fuel injector
fluidly connected with the source of high pressure actuation fluid;
a viscosity sensor for determining the viscosity of the high
pressure hydraulic actuation fluid; and, a controller in
communication with the hydraulically actuated fuel injector being
adapted to determine a rate in change of the viscosity, wherein the
controller is adapted to responsively produce a fuel injection
command signal in response to the rate of change of the viscosity
of the high pressure hydraulic actuation fluid.
9. A fuel injector system, as set forth in claim 8, further
comprising: an engine speed sensor adapted to sense an engine
speed, and responsively produce an engine speed signal; and, a
temperature sensor for determining the temperature of the high
pressure hydraulic actuation fluid, wherein the controller being
adapted to receive the output from the engine speed sensor and the
temperature sensor, and the controller responsively determines a
shear rate adjustment.
10. A fuel injection system, as set forth in claim 9, wherein the
controller is adapted to determine a rate of fuel consumption, and
to determine a rate of change of the viscosity in response to the
engine speed signal and the rate of fuel consumption.
11. A fuel injection system, as set forth in claim 10, wherein the
controller is adapted to determine an injection command signal in
response to the rate of change of the viscosity and the shear rate
adjustment.
12. A fuel injection system, as set forth in claim 10, wherein the
controller further comprises at least one of a plurality of
predetermined viscosity maps as a function of the engine speed and
the rate of fuel consumption, the rate of change of the viscosity
being determined in response to the at least one predetermined
viscosity maps.
13. A fuel injection system, as set forth in claim 10, wherein the
controller further comprises at least one of a plurality of
predetermined viscosity tables being a function of the engine speed
and the rate of fuel consumption, wherein the rate of change of the
viscosity being determined in response to the at least one
predetermined viscosity tables.
14. A fuel injection system, as set forth in claim 10, wherein the
controller further comprises at least one of a plurality of
predetermined shear rate maps being a function of the high pressure
actuation fluid temperature, the engine speed, and the viscosity of
the high pressure actuation fluid, wherein the rate of change of
the viscosity being determined in response to the at least one
predetermined maps.
15. A fuel injection system, as set forth in claim 10, wherein the
controller further comprises at least one of a plurality of
predetermined shear rate tables being a function of the high
pressure actuation fluid temperature, the engine speed, and the
viscosity of the high pressure actuation fluid, wherein the rate of
change of the viscosity being determined in response to the at
least one predetermined tables.
Description
TECHNICAL FIELD
The present invention relates generally to a fuel injection system
having at least one hydraulically actuated fuel injector and, more
particularly to controlling a supply of high pressure actuating
fluid to the injector.
BACKGROUND ART
In a fuel system having hydraulically actuated electronically
controlled unit injectors, such as HEUI injectors available from
Caterpillar Inc., high pressure hydraulic actuating fluid drives a
plunger to pressurize fuel and thereby inject high pressure fuel
from a nozzle. An electronic activator, such as a solenoid, or a
piezo-electric device, controls when the high pressure actuating
fluid is exposed to the plunger. The amount of fuel injected is
controlled by adjusting the duration the electronic actuator is
"on".
The viscosity of the actuating fluid effects both the amount of
fuel delivered by the injector, and when the fuel pressurization
process begins. For example, at cold temperatures the actuating
fluid is thicker (more viscous) than at warm temperatures.
Therefore, when an electrical signal is delivered to an electronic
actuator, the fluid flows into the injector at a relatively slow
rate, to drive the plunger. With the actuating fluid moving at a
relatively slow rate, there is an increased delay before the
injector begins delivering fuel. Furthermore, when the electronic
actuator is turned off to stop delivery of the fuel, the reduced
flow rate of the actuating fluid results in less than the intended
amount of fuel being injected. Hence, with a high viscosity
actuating fluid as seen at cold starting temperatures as compared
to higher temperature operating conditions, the fuel injection
event occurs later than intended due to the slower delivery rate of
the actuating fluid. Under these conditions, overall engine
performance may be adversely effected, resulting in incomplete
combustion, low power, white smoke, unused particulate matter, and
NOx.
The viscosity of the actuating fluid is a function of the fluid
type, the temperature of the fluid, and the shear rate of the fluid
in the hydraulic circuit. In an operating engine, neither the type
of fluid, the shear rate, nor the temperature is fixed. The fuel
system may use a variety of actuation fluids. For example, a more
viscous SAE 15W40 engine oil or a less viscous0W20 engine oil may
be used. Also the fuel system operates over a wide range of
temperatures, e.g., -45.degree. C. through 120.degree. C.
The viscosity of the actuating fluid changes with a change in shear
rate at a given temperature. During cranking at either hot or cold
starting conditions, the viscosity of the actuating fluid is
temporarily lowered when the flow rate of the fluid is increased
and the well sheared actuating fluid enters the actuating fluid
circuit. The temporary viscosity loss can not be detected by the
engine governor or the vehicle operator. The sudden, temporary loss
of viscosity produces a sudden increase in fuel delivery, which in
turn creates a rapid change in engine speed.
The reduction in fuel delivery and delays in timing increase as the
viscosity of the actuating fluid increases. If the changes in shear
rate, which temporarily change the viscosity, are not accounted
for, the fuel delivery and timing may be incorrect making it
difficult to start and run the engine especially at high
viscosities encountered at cold temperatures. If the fuel delivery
is too small, or is not delivered at the proper time, the engine
may not start or be underpowered. If the fuel delivery is too large
the engine structural capabilities may be exceeded, excessive smoke
may be produced, and misfire may occur.
The present invention is directed to overcoming one or more of the
problems identified above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a method or operating a
fuel injection system including at least one hydraulically actuated
fuel injector fluidly connected with a source of high pressure
hydraulic actuation fluid is disclosed. The method includes the
steps of determining the viscosity of the actuation fluid, the rate
of change of the viscosity, and controlling the supply of actuation
fluid to the fuel injector based, at least in part, on the
determined viscosity of the actuation fluid.
In another aspect of the present invention a fuel injection system
is disclosed. The fuel injection system includes at least one
hydraulically actuated fuel injector fluidly connected with the
source of high pressure actuation fluid, a viscosity sensor for
determining the viscosity of the high pressure hydraulic actuation
fluid, and a controller in communication with the hydraulically
actuated fuel injector being adapted to determine the rate in
change of the viscosity of the high pressure actuating fluid, and
determining a fuel injection command signal in response to the rate
of change of the viscosity of the high pressure hydraulic actuation
fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic illustration of a fuel system of an engine
with which this invention may be used; and
FIG. 2 is an illustration of the method for controlling a fuel
injection timing of a fuel injector.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a fuel injection system having at
least one hydraulically actuated fuel injector. FIG. 1 is an
illustration of one embodiment of a fuel system 105 of an engine
110. The fuel system 105 includes at least one fuel injector 115a-f
for each combustion chamber or cylinder of the fuel system 105. In
the preferred embodiment, the fuel injectors are hydraulically
actuated electronically controlled unit injectors, such as HEUI
injectors available from Caterpillar Inc. Each injector 115a-f has
an associated solenoid (not shown). In FIG. 1, six unit injectors
115a-f are shown, however, the present invention is not limited to
use in connection with a six cylinder engine. To the contrary, it
may be easily modified for use with an engine having any number of
cylinders and unit injectors 115. In addition, this invention may
also be used with unit pump rather than unit injector fuel
systems.
The fuel system 105 also includes a circuit 120 for supplying
actuating fluid to each injector 115. Actuating fluid is required
to provide sufficient pressure to cause the unit injectors 115 to
open and inject fuel into an engine cylinder. In one embodiment the
circuit 120 includes a high pressure pump 125, driven by the
internal combustion engine 110. The output of the pump 125 is
connected to each fuel injector 115. Low pressure actuating fluid
is pumped from the sump 130 by a low pressure pump 135 through a
filter 140, which filters impurities from the fluid. Each injector
115 is also connected to the fluid sump 130 in order to return the
actuating fluid to the fluid sump 130.
The circuit 120 may include an actuation pressure control valve 145
for regulating the pressure of actuating fluid in the rail in cases
where the pump 123 is a fixed delivery pump. Alternately, the pump
125 may be a variable delivery pump, thereby obviating the
actuation pressure valve 145. A check valve 150 is also
provided.
The fuel system 105 includes an engine speed sensor 155. In one
embodiment, the speed sensor 155 reads the signature of a timing
wheel applied to the engine camshaft to indicate the engine's
rotational position and speed. The engine speed sensor 155 monitors
the rotational position of the crankshaft relative to top dead
center position and bottom dead center position of the respective
cycle or stroke. Other devices for determining the engine speed,
such as an accelerometer sensor (not shown), may be substituted.
The engine speed sensor 155 generates a speed signal.
The circuit 120 also includes a temperature sensor 160. The
temperature sensor 160 senses the temperature of the actuating
fluid, and responsively generates a fluid temperature signal. In
one embodiment the actuating fluid is petroleum based oil. However,
the fluid may be a synthetic oil, fuel, or other type of
non-compressible fluid.
The circuit 120 also includes a viscosity sensor 165. The viscosity
sensor 165 senses the viscosity of the actuating fluid and
responsively generates a viscosity signal. Typically, the viscosity
sensor 165, is located proximal to the pump 125, preferably on the
input side for the actuating fluid.
The circuit 120 includes a pressure sensor 170. The pressure sensor
170, is typically located between the pump 125, and the injectors
115. The pressure sensor 170 senses the pressure of the actuating
fluid in the rail and responsively generates a pressure signal.
The fuel system 105 also includes an electronic control module 175.
The controller 175 receives the plurality of generated signals and
responsively determines the injection timing for the fuel injectors
115a-f. The controller 175 delivers an injection command signal to
the solenoid of the appropriate injectors 115. The controller 175
contains software decision logic, a plurality of software look-up
tables and/or maps, and information defining the fuel system
operational parameters and controls key components accordingly. The
injectors 115a-f are individually connected to outputs of the
controller 175 by electrical connectors 180a-f respectively.
The present invention includes a method for controlling the fuel
injection timing of a fuel injector 115 during engine starting and
idle operating conditions. The method includes the steps of
cranking the engine 110, determining the engine speed, the
temperature of the actuating fluid, the viscosity, and the rate of
change in the viscosity of the actuating fluid. A shear rate
adjustment is determined based on the engine speed, temperature,
and viscosity of the actuating fluid. The shear rate adjustment
factor and the engines current operating conditions are utilized by
the controller 175 in responsively determining injection timing.
FIG. 2. illustrates a flow diagram of the present invention.
In a first control block 205, the engine speed is sensed by the
engine speed sensor 155. An engine speed signal is produced and
delivered to the electronic controller 175.
In a second control block 210, the temperature of the actuating
fluid is sensed by the temperature sensor 160, and a temperature
signal indicative of the temperature of the actuating fluid is
delivered to the controller 175.
In a third control block 215, the viscosity of the actuating fluid
is sensed by the viscosity sensor 165, and a viscosity signal
indicative of the viscosity of the actuating fluid is delivered to
the controller 175. Viscosity sensors that can be used in the fuel
injection system for producing signals indicative the fluid being
sensed, are well know in the art. One example of a viscosity sensor
that may be used is the type that determines viscosity as a
function of the pressure drop of a fluid flow over an orifice. Some
other examples of sensors that may be used are that type using
ultra sonic waves to determine viscosity, or the viscosity
detection device disclosed in U.S. Pat. No. 5,896,841.
In a fourth control block 220, the rate of change in the viscosity,
specifically a gradual change versus a step change, is determined.
The rate of change in viscosity can be calculated or can be
determined by a table/map based on actuating fluid consumption rate
and engine idling conditions such as engine load. An actuating
fluid consumption rate is a function of the amount of fluid in the
actuating fluid circuit 120 between the pump 125 and the injectors
115a-f, the engine speed, and the current injection delivery time.
The rate of change in viscosity is used to determine when the
sheared down oil will reach the injectors. The greater the shear
rate in the actuating fluid is, the greater the rate of change in
the viscosity of the actuating fluid will be.
In a fifth control block 225, a shear rate adjustment associated
with the change in viscosity due to fluid shear rate change is
determined. In one embodiment, the shear rate adjustment is
determined from maps or look-up tables illustrating the shear rate
adjustment relative to a given actuating fluid temperature as a
function of engine load. In another embodiment the shear rate
adjustment may be dynamically calculated.
Each of the shear rate adjustment maps or tables, for a given fluid
temperature, contains empirically obtained data for a plurality of
viscosity measurements taken during engine operating conditions
from zero to full engine load. A map/table can be produced for each
actuating fluid temperature at 5.degree. increments in a range of
-45.degree. C. through 120.degree. C. The temperature range and
increments are dependent on the size and type of engine, and that
engines operating parameters.
Table 1 shown below illustrates one embodiment of a shear rate
adjustment table. Table 1 has data for determining the shear rate
adjustment associated with viscosity measured in the actuating
fluid circuit 120 at a range of engine loads, for a given
temperature. For the table below: "X" is a temperature in the range
of -45.degree. C. to 120.degree. C.; "v" is the measured viscosity
of the actuating fluid; "Engine Load" is in increments from zero to
full engine load; and ShrAdj is the shear rate adjustment.
TABLE 1 Temperature X.degree. C. Engine Engine Engine Engine Load
#1 Load #2 Load #3 . . . Load #n v1 ShrAdj 11 ShrAdj 12 ShrAdj 13
ShrAdj 1n v2 ShrAdj 21 ShrAdj 22 ShrAdj 23 ShrAdj 2n v3 ShrAdj 31
ShrAdj 32 ShrAdj 33 ShrAdj 3n . . . vn ShrAdj n1 ShrAdj n2 ShrAdj
n3 ShrAdj nn
The shear rate adjustment tables/maps are stored in the electron
controller 175. During the operation of the present invention, the
controller 175 receives the engine speed signal, the fluid
temperature signal, the and the fluid viscosity signal.
In a sixth control block 230, an injection command signal is
produced by the controller 175 in response to the engine speed, the
temperature and viscosity of the actuating fluid, the viscosity
rate of change, and the shear rate adjustment. The control loop
will be repeated for each injection cycle. In this manner, the
injection timing may vary in accordance with the temporary
viscosity change due to fluid shear rate change during hot or cold
engine starting and idle conditions.
Other aspects, objects, and advantages of the present invention can
be obtained from a study of the drawings, the disclosure, and the
claims.
Industrial Applicability
The present invention provides an apparatus and method for
controlling the fuel injection timing of a fuel injector during
engine starting and idle operating conditions. In the preferred
embodiment the fuel injector is a hydraulically-actuated unit
injector (HEUI).
The engine speed is sensed and an engine speed signal indicative of
the engine speed is generated. The temperature of the actuating
fluid is sensed and an actuating fluid temperature signal is
generated. A rate of change in viscosity, be it a gradual change or
a step change, is determined based on engine speed, actuating fluid
temperature and viscosity. A shear rate adjustment is determined
dependent on the rate of change of the viscosity. The injection
timing, the time the injection starts or the duration of the
injection is adjusted in accordance with the shear rate adjustment
and current engine operating parameters.
Other aspects, objects, and advantages of the present invention can
be obtained from a study of the drawings, the disclosure, and the
claims.
* * * * *